Method and apparatus for composting organic material

ABSTRACT

The present invention relates to a method for composting organic material, in which method organic material is transported to a bioreactor ( 1 ) where it is mixed and where material for regulating the oxygen content and bacteria and/or enzymes for agitation of composting process are added to it, and where organic material may compost, after which the composted material is removed outside the bioreactor to be stabilized. The invention also relates to a device for composting organic material, which device includes a bioreactor ( 1 ) with at least one filling and emptying opening ( 12, 13, 17 ) in order to fill and empty the bioreactor, and a transporting device ( 2 ) mixing the material inside the bioreactor ( 1 ) in order to transport the organic material to be composted and to mix it inside the bioreactor. Characteristic to the method in accordance with the invention is that organic material is transported by means of a mixing transporting device ( 2 ) upwards and then dropped down against a spreading element ( 16 ) and from there back to the transporting device thus spreading the organic material to a smaller particle size and the particles while falling down come into contact with oxygen and moisture of the air in the bioreactor ( 1 ). Characteristics to the device in accordance with the invention is that the bioreactor ( 1 ) includes a turning element ( 11 ) to direct the organic material to be transported with a transporting device ( 2 ) upwards and back to mainly opposite direction in respect with the transporting direction of the transporting device.

[0001] The present invention relates to a method for composting organicmaterial, in which method organic material is transported to abioreactor where it is mixed and where material for regulating theoxygen content and bacteria and/or enzymes for agitation of compostingprocess are added to it, and where organic material may compost, afterwhich the composted material is removed outside the bioreactor to bestabilized. The invention also relates to a device for compostingorganic material, which includes a bioreactor with at least one fillingand emptying opening in order to fill and empty the bioreactor and amixing transporting device mixing the material inside the bioreactor inorder to transport the organic material to be composted and to mix itinside the bioreactor.

[0002] There are various methods today for composting organic material,such as biowaste and biomass and various devices to be employed whileusing them. Such devices are, for example, tunnel composters, drumcomposters and silo composters. The material to be composted in thesecomposters is fed to the composter after which the composter is keptunder certain circumstances such that the composting process begins andproceeds in a functional way. Air is fed to the composter during theconi-posting process in some today recognized composters. This promotesthe oxygen supply and the composting process.

[0003] Current composting methods are functional as such but thecomposting process continues for a relatively long period of time whileemploying them (usually several weeks) and is difficult to becontrolled. Furthermore, while using currently known composting methodsorganic material composts heterogeneously and the proceeding of thestages of the process and the hygienesafion may not be verified.Furthermore, there is, for example, a bad odour control in currentcomposting methods and in special cases actual health hazards are causedto those working in connection with a composter.

[0004] The purpose of the invention is to provide a method and a devicefor composting organic material, which eliminate earlier mentioneddisadvantages. Especially the purpose of the invention is to provide amethod, which promotes organic material to compost clearly faster, morehomogeneously and more flexibly than earlier and in which it is possiblyto verify the proceeding of the composting process. Furthermore, thepurpose of the invention is to provide a device, which is relativelysimple and profitable and by employing of which the verifying of thehygienesation is managed to carry out reliably and simply.

[0005] The object of the invention is accomplished by a method and adevice for composting organic material, the characteristics of which arepresented in the claims.

[0006] Characteristic to the method in accordance with the invention isthat organic material is transported by means of a mixing transportingdevice upwards and then dropped down against a spreading element andfrom there back to the transporting device thus spreading the organicmaterial to a smaller particle size and the particles while falling downcome into contact with oxygen and moisture of the air in the bioreactor.This is how particles of the organic material gain oxygen and moistureall the time evenly and the composting of organic material proceedsquickly and simultaneously in the whole material amount. Due to this itis possibie to make organic material to decompost in clearly shorterperiod of time than while using earlier recognised methods and the rawcompost is of higher quality and it is composted more homogeneously.

[0007] In an advantageous application of the method in accordance withthe invention the organic material in a bioreactor is transported by amixing transporting device against a hemispherical wall such, that thematerial turns following a spherical course upwards and falls back tothe direction mainly opposite with respect to the transporting directionand downwards. Furthermore, the fallen organic material is directedagainst the wall opposite to the spherical wall, which is splitting thematerial in the bioreactor. This way it is possible to mix the organicmaterial and to decompost it into material with a smaller particle sizeevenly and completely so that the supply of oxygen and moisture of theparticles while falling is as even and efficient as possible.

[0008] In the second advantageous application of the method inaccordance with the invention organic material is mixed in certain fimeintervals for suitable mixing periods. This way the microbiologicalfunctioning and the increasing of temperature due to it may becontrolled such that the composting is possible to realize asefficiently and quickly as possible.

[0009] In the third advantageous application of the method in accordancewith the invention the moisture content inside the bioreactor isadjusted during the composting process. A presumption of an efficientcomposting is, among other things, a suitable moisture content. By meansof the moisture control devices of the bioreactor in accordance with themethod the moisture content of the air in the bioreactor may he keptoptimum the way other factors having influence on the decomposting ofthe organic material require. This is the way the best circumstances forthe moisture content of the air are reached which, for its part,accelerates and increases the efficiency of the biological decompostingof the organic material.

[0010] In the fourth advantageous application of the method inaccordance with the invention the acidity of the organic material isadjusted by measuring the ph-value of the organic material and by addingacidity regulating material to the bioreactor. Acidity of the organicmaterial has influence on the functioning of bacteria decomposting thematerial. This is why by adding lime, for example, or some othersuitable acidity control material the ph-value is possible to be kept assuitable as possible and the composting proceeds as efficiently andcompletely as possible also in terms of acidity.

[0011] Characteristic to the device in accordance with the invention isthat the bioreactor includes a turning element to direct the organicmaterial to be transported by the mixing transporting device upwards andback mainly to the opposite direction in respect with the transportingdirection. Due to the turning element the organic material to becomposted may be mixed in accordance with the method in a simple,reliable and profitable way such that all particles of the material comeinto contact with oxygen and moisture in the air.

[0012] In an advantageous application of the device in accordance withthe invention the turning element is a hemispherical end wall of abioreactor. This way it is possible to have a turning element directingthe organic material in accordance with the method in accordance withthe invention in the bioreactor simply and profitably without installingseparate parts inside the bioreactor. Furthermore, due to this kind ofan end wall there will be no corners gathering material in the joiningpoints between the end wall of the bioreactor and other walls, whereorganic material to be composted could stick and clod.

[0013] In the second advantageous application of the device inaccordance with the invention there is a spreading element in thebioreactor in order to spread the material directed by the turningelement. Due to the spreading element the organic material is spreadinto particles of a small size and stays that way during the wholecomposting process. Due to this it is possible to control the supply ofoxygen and moisture of all particles of the organic material evenly andcontrolled.

[0014] In the third advantageous application of the device in accordancewith the invention the spreading element is a mainly v-shaped wallviewed from above, attached in diagonal position inside the bioreactor.A spreading element realized this way is simple and economical tomanufacture. Furthermore, it is easily possible to manufacture this kindof a spreading element such that in it or due to it in other parts ofthe bioreactor there will be no such places which could gather or clodmaterial such as different kinds of comers or hollows. Furthermore, itis possible to direct the organic material easily to desired directionwhile using this kind of spreading element, for example, back inside thebioreactor to the transporter.

[0015] In the fourth advantageous application of the device inaccordance with the invention there is a composting part and a cleaningpart inside the bioreactor and a spreading element is a separating wallbetween the composting part and the cleaning part. This way it ispossible to make the inside of the bioreactor simple and economical tomanufacture. Furthermore, this way there are less places which areseparate from the walls and would easily gather and clod material insidethe composting part and there is no need to build any special separatingwall between the composting part and the cleaning part.

[0016] Next, the invention will be explained in more detail withreference to the accompanying drawings, in which,

[0017]FIG. 1 illustrates a device in accordance with the method inaccordance with the invention viewed from side, and

[0018]FIG. 2 illustrates a device in accordance with FIG. 1 viewed fromahead.

[0019] The device in FIGS. 1 and 2 includes a turnable, in inclinedposition on a suitable base attached bioreactor 1. It is areservoir-like apparatus, which has been constructed from a conical part10 closed with a vertical wall in the narrow end and a hemispherical endwall 11 functioning as a turning element and placed in the wider end.Both parts are, in this case, manufactured of a stainless Steel plate,which has been insulated on the outer surface with, for example,polyurethane. There is a bottom part 7 in the lower part of thebioreactor, a part of which is an emptying opening 17 with openableemptying hatches 8 and 9. There is a transporter 2 mixing material andconstructed from screws 3-6 placed near the bottom part in the lowerpart of the bioreactor. The inside of the bioreactor has been dividedinto a composting part 14 and a cleaning part 15 with a separating wall16. For filling the composting part 14 with organic material there is afilling opening 12 of the composting part in the upper part of it.Correspondingly there is a filling opening 13 of cleaning part foradding the eleaning material in the cleaning part 15. As illustrated inFIG. 1 the filling openings 12 and 13 are equipped with square incrosssection pipe collars and closing plates located in the lower partof the pipe collars to make the filling easier and to close the fillingopening during the composting process. There is an opening in the lowerpart of the composting part 14 where the screws are which is as broad asthe screws 3-6 and as long as the thread part of the screws and theopening is covered with a bottom part 7 following the shape of thescrews under the screws as illustrated in FIG. 2. Emptying of theorganic material is carried out, in this application, through theemptying hatches 8 and 9 joined with hinges to the emptying opening 17of the bottom part 7. Furthermore, the device in accordance with FIGS. 1and 2 includes an inclining device (not illustrated in FIGS. 1 and 2).It includes an inclining mechanism functioning by means of hydrauliccylinders in order to incline the bioreactor, for example, into inclinedposition in accordance with FIG. 1. In the application in accordancewith FIG. 1 the angle of inclining may be regulated from horizontalposition to about 40′ angle. The base of the device is a recognized baseconstruction, by means of which the bioreactor with accessories may heattached to a desired location in a functional manner.

[0020] The transporter 2 mixing material of the device in accordancewith FIGS. 1 and 2 has been constructed of screws 3-6. The screws are,in this application, recognized transporting screws for material run byan electric motor and they are mounted in bearings to the lower part ofthe reactor in accordance with FIG. 1. The threads of the screws 3 and 4are of the same direction and in the opposite direction with the threadsof the screws 5 and 6. The direction of the thread in all screws hasbeen chosen such that the material fed to the composting part movestowards the end wall 11 and from the sides to the centre.

[0021] In the device in accordance with FIGS. 1 and 2 the turningelement in accordance with the method is a hemispherical end wall 11 ofthe bioreactor. By means of it the material transported by the screws3-6 may be turned inside the bioreactor through the upper part back tothe narrower end of the bioreactor. Due to the spherical shape thematerial turns back also in the direction of the longitudinal axis ofthe screws as well as in the directions between the longitudinal and thetransversal axes. This way the device in accordance with FIGS. 1 and 2mixes the organic material such, that the material rises upwards andfalls against the separating wall 16 and moves back from there to thescrews 3-6. While falling the particles of the organic material to becomposted come into contact with oxygen and moisture of the air in thebioreactor. The moisture content of the air in the bioreactor iscontrolled by the regulating and controlling system of the device suchthat the falling material always gains oxygen and moisture in suitableamount. The device includes, in accordance with the method in accordancewith the invention, a spreading element in order to spread the materialinto a suitable small particle size. The separating wall 16 between thecomposting part 14 and the cleaning part 15 represents the spreadingelement in this application. For this reason it has been designed to bev-shaped viewed from above such that the point of the v-shape ispointing to the direction of the composting part (transporting directionof the screws). This way the organic material inside the composting partis split mainly into two flows heading for the sides while fallingagainst the separating wall 16. This crushes and spreads possiblematerial clods and lumps into a smaller size thus keeping the material,in respect with the oxygen and moisture supply, in advantageous formwith a small particle size.

[0022] Regulating and controlling system (not illustrated in FIGS. 1 and2) includes, in this case, an air supply system, a measuring equipmentfor oxygen and moisture content and for temperature, a computer, acontrolling and measuring card installed into the computer as well as asuitable computer programme to control various functions in an earlierdetermined manner. The probes measuring oxygen and moisture contents aswell as temperature of the organic material to be composted have beenplaced in suitable places inside the bioreactor and connected to theearlier mentioned measuring and controlling card. By means of the airsupply system (not illustrated in FIGS. 1 and 2) controlled by thecomputer it is possible to supply air into the bioreactor and to controlthe moisture content of the air in the bioreactor in accordance with anearlier determined moisture curve. This way it is possible to have asideal circumstances as possible for the decomposting of material inrespect with the oxygen and moisture content of the air in thebioreactor.

[0023] There is an air supply opening constructed to a side of theconical part 10 of the bioreactor 1 for the air supply system to whichopening an air supply channel being a part of the system has beenconnected and to the opposite side to the other side of the conical partan outlet has been constructed to which the air outlet channel has beenconnected. The air supply channel has been connected to a fan equippedwith a dehumidifier and the outlet channel has been connected to afilter. The dehumidifier has a recognized construcfion to removemoisture from the air to be blown to the air supply channel. The filteris, in this case, a so-called biofilter, which is an earlier recognizedconstruction. Hazardous organic gases possible been created in theoutlet air which otherwise would cause earlier mentioned bad odourrelated to earlier recognized equipment may be removed from the air inthe bioreactor by means of it.

[0024] While employing the device in accordance with FIGS. 1 and 2 thecomposting part 14 of the bioreactor is filled tbrough the fillingopening 12 with some suitable compostable organic material. These arevarious biomasses, such as organic waste from food manufacturingindustry and organic community waste. After this the material forregulating the oxygen content is added to the composting part 14, whichmaterial is some rough material such as sawdust, which increases theoxygen content of the organic material to be composted in a suitablemanner. Next the reactor part is turned to a suitable inclined positionand the screws 3-6 functioning as a mixing transporter 2 are started andthe organic material and the material for regulating the oxygen contentbegin to mix. Mixing continues for some time in this stage, usually fromhalf an hour to an hour, after which mixing is stopped for a while.Suitable aerobic bacteria depending on the material to be composted maybe added to the material to be composted during the mixing process toagitate the composting process. After starting the mixing also theregulation of the oxygen and moisture content is started by means of theair supply system. This is carried out by blowing air (which may bemoisturized while needed) to the bioreactor through the air supplychannel in accordance with the earlier determined programme which is apart of the regulating and controlling system taking account of thecontinuous measurements of oxygen and moisture contents as well astemperature in the bioreactor. After the first mixing stage the screwsare stopped and the composting circumstances are regulated. To keep theair supply in needed level the screws and the air supply system arestarted and run in suitable periods (usually about 10 min. at intervaisof an hour). The suitable duration of periods is determined by theresults from the measuring probes such that the oxygen and moisturecontent and the temperature will stay on the planned level. This stageis carried out until the temperature and the duration in thistemperature according to the requirements for the composting of thiscomposting material are achieved. The regulating programme in use may bechosen with respect to the content of the organic material to becomposted from the programme library saved in the memory of a computer.Usually the oxygen content is kept constant and the moisture content isregulated in respect with the organic material in accordance with aearlier determined moisture curve. The temperature may not be regulateddirectly but the regulation of the temperature is carried out indirectlyby means of other regulating measures. Too great an increase intemperature has a slowing effect on bacteria activity so the mosteffective decomposting is achieved in temperature depending on theproceeding of the composting process and the bacteria in use. Usually inthe end of the composting process the temperature of 55-800 C. isachieved. This stage (so called raw compost) is achieved in 20-30 hoursafter filling the device using suitable bacteria. After this theemptying hatches in the bottom part are opened and the bioreactor isemptied by using the screws to a suitable transporter, for example,which transports the material to be stabilized in a suitable place suchas to a pile outdoors made for this. After stabilizing the compostedmaterial is ready to use as desired, for example, as plant fertilizer.

[0025] The method in accordance with the invention may differ in manyways from the above mentioned example application. It may comprise, forexample, stages realized in different ways and with different compostingparameters and duration. Furthermore, in some applications thecontrolling of the process in accordance with the method may comprise,for example, measurements and regulations of various parameters. Theregulation of acidity of the material to be composted based on pHmeasurements is one of those. In that case the acidity of the organicmaterial is regulated by adding suitable acid control agent to thebioreactor. The input of the acid control agent may be organized tooccur automatically or it may be carried out manually based oncalculations and instructions of the computer of the device.

[0026] The device in accordance with the method in accordance with theinvention may also be realized in many ways differing from the exampledevice illustrated in FIGS. 1 and 2. For example, the shape, size andthe material of the parts of the bioreactor as well as the number, sizeand the thread of the screws of the mixing part may vary. The conicalpart of the bioreactor, the hemispherical end wall, the filling andemptying hatches as well as the separating wall as a spreading elementmay be constructed of some other suitable material such as various kindsof alloys, aluminium, composite materials or some suitable plasticinstead of a stainless steel plate. The angle and position of theseparating wall functioning as a spreading element between thecomposting part and the cleaning part may vary from the position in FIG.1, for example, depending on for what kind of materials the device inquestion is meant and on what speed this material is transported andmixed inside the bioreactor. Naturally, the spreading element as well asthe turning element may be separate parts from the wall of thebioreactor placed inside the composting part in some applications. Alsoother parts of the device may be by construction realized as desireddiffering from the application in FIGS. 1 and 2 such that by means ofthem a functional device is provided to realize a method in accordancewith the invention.

[0027] The invention is not limited to the presented advantageousapplication but it can vary within the frames of the idea of theinvention formed in the claims.

1. A method for composting organic material, in which method organicmaterial is transported to a bioreactor (1), where it is mixed, andwhere the material regulating the oxygen content and bacteria and/orenzymes for agitation of composting process are added to it and whereorganic material may compost, after which the composted material istransported for stabilization outside the bioreactor, characterized inthat the organic material in the bioreactor (1) is transported by themixing transporting device (2) upwards against the hemispherical wall(11) such, that the material turns following mainly spherical courseupwards and falls down to the direction mainly opposite in respect withthe transporting direction and down, and that the fallen organicmaterial is directed against the wall (16) splitting the material andwhich is opposite the hemispherical wall (11) of the bioreactor (1) andfrom there back to the transporting device thus spreading the organicmaterial to a smaller particle size and the particles while falling downcome into contact with oxygen and moisture of the air in the bioreactor(1).
 2. A method in accordance with claim 1, characterized in that theorganic material is mixed in certain intervals for suitable mixingperiods of time.
 3. A method in accordance with any of claims 1 or 2,characterized in that the moisture content of the air inside thebioreactor (1) is regulated during the composting.
 4. A method inaccordance with any of claims 1-3, characterized in that the acidity ofthe organic material is adjusted by measuring the pH-value of theorganic material and adding acidity regulating material to thebioreactor (1).
 5. A device for composting organic material, whichincludes a bioreactor (1), with at least one filling and emptyingopening (12, 13, 17) to fill and to empty the bioreactor, and a mixingtransporting device (2) for the material inside the bioreactor (1) forand mixing the organic material to be composted inside the bioreactor,characterized in that the bioreactor (1) includes a hemispherical wall(11) to direct the organic material to be transported with thetransporting device (2) upwards and back to direction mainly opposite inrespect with the transporting direction of the transporting device, andthat the bioreactor (1) includes a wall (16) splitting the material andwhich is opposite the hemispherical wall (11), to spread the fallingmaterial to a smaller particle size and to direct it back to thetransporting device (2).
 6. A device in accordance with claim 5,characterized in that the wall (16) splitting the material is a mainlyv-shaped wall which is attached inside the bioreactor (1) in such a waythat the sharp end of the wall points mainly to the transportingdirection of the transport device (2).
 7. A device in accordance withclaim 5 or 6, characterized in that inside the bioreactor (1) there is acomposting part (14) and a cleaning part (15) constructed, and that theseparating wall between the composting part (14) and the cleaning part(15) is employed as a wall (16) splitting the material.